Study On Mechanism Of Pepsin Degradation Of Soybean Protein Isolate Emulsion Under Interface System

In this study,soy protein isolate as a component interface,and acts as an emulsifier and stabilizer in the emulsion.Mechanism of pepsin degradation of soybean protein emulsion at the interface of the system was studied in the simulated gastric fluid.This study includes Preparation of SPI,the SPI emulsion and artificial gastric juice model,optimization of two-dimensional electrophoresis system.Characteristics of An Oil-in-Water Emulsion Stabilized by SPI in an in vitro gastric model and proteomic analysis.Soy protein isolate can get through alkali solution and acid extraction,protein content can reach 91 ± 0.5%,the extraction rate was 27 ± 0.9%.In this study,soybean protein isolate(SPI)adsorbed on the oil-water interface to form a O/W(oil in water)emulsion as emulsifier and stabilizer.The Characteristics of SPI-stabilized emulsions(2.0 wt% protein and20.0 wt% soy oil)under the action of simulated gastric fluid(37?,pH 1.2 and 34 mM NaCl ionic strength,with continus shaking at approximately 95 rev/min for 2 h)was investigated.Changes in particle size,Zeta-potential and microstructure were monitored as a function of incubation time in the simulated gastric fluid.Initially,SPI formed a stable emulsion,but the emulsion underwent extensive droplet flocculation,with some coalescence,on mixing with the gastric fluid.The droplet flocculation and the coalescence observed during hydrolysis were markedly dependent on the action time.The Zeta potential values gradually changed from?35.9±0.3 mV to ?16.3±0.9 m V after the emulsion mixed with simulated gastric fluid.When SPI was present at the interfacial layer of the oil-in-water emulsion,it was easier hydrolysed by pepsin than native SPI solution,as shown by SDS-PAGE.The results of emulsion physical properties test show that the emulsion consistency first and then increase the same state,the emulsion viscosity first increased,then decreased,and maintain a stable state in the artificial gastric juice model.We found a total of1218 kinds of proteome between the isolated Soybean Protease and hydrolysis of isolated soy protein solution after 20 min and after 90 min solution though LC-MS identified in the three lanes.Soy protein isolate emulsions initially held steady,after adding pepsin digestion by pepsin,the emulsion through to a steady-state process,and then more difficult digested protein or peptide group after stirring,and then will go through a emulsification process,maintain homeostasis.Accordingly,depending on the application(such as controlling coating material release time)design protein food emulsions can be coated to control object(grease,etc.)in the body of the release point.This study can improve people's understanding of the O/W emulsion degradation characteristics of SPI based on simulated gastric fluid model.For the design of soy protein emulsion and then regulate the emulsion coating material(oil,etc.)to provide methodological basis,and have a big significance in the design of SPI emulsion-based food systems.